The invention described herein relates to method and apparatus for quantitatively monitoring trace impurities in flowing gases through the reaction of the impurities with electronically metastable atoms or molecular species produced in the afterglow of a flowing plasma.
There are many situations in which it is necessary to rapidly and effectively monitor the content of trace impurities in flowing gases. The high temperature gas-cooled reactor (HTGR) is an example of a system in which such monitoring is imperative. The coolant gas flowing through the primary loop of the HTGR is helium. The helium in the primary loop may be contaminated with water vapor from the secondary side of the heat exchangers or from the helium circulator bearings. Reactions of water with the hot graphite fuel blocks or core support structure of the reactor through which the coolant helium flows are highly deleterious. As a consequence, it is imperative that the moisture level in the primary loop be measured accurately on a continuous basis. Preferably, the monitoring method and apparatus should be capable also of quantitatively measuring reaction products of the water and the hot graphite as, e.g., CO, CO.sub.2, and CH.sub.4.